1. Field of the Invention
The present invention relates to a design of an LED lamp holder, particularly to an LED lamp capable of adjusting a beam spread thereof.
2. Description of the Related Art
Referring to FIG. 1, a conventional LED lamp whose projecting and condensing module could be freely replaced is disclosed by a Taiwan patent No. M356844. The disclosure comprises a casing unit 11 with an accommodating room 111, a circuit unit 12 disposed within the accommodating room 111, a projecting unit 13 installed in the accommodating room 111, and a detachable cover unit 14 mounted on the casing unit 11. Wherein, the circuit unit 12 includes a holding plate 121 and at least one LED member 122 disposed on the holding plate 121. Moreover, the projecting unit 13, disposed on the holding plate 121, includes at least one projecting member 131 corresponding to the LED member 121. Further, the cover unit 14 includes a lens 141, a gasket 142, a separable inner cover 143 spirally engaged with the casing unit 11, and a removable outer cover 144 spirally engaged with the casing unit 11 for compactly propping against the inner cover 143. Herein, the inner cover 143 has a first aperture 145, and the outer cover 144 has a second aperture 146 corresponding to the first aperture 145. Additionally, the gasket 142 is placed between the casing unit 11 and the inner cover 143 for providing the lens 141 with a tight joint to the projecting unit 13. Thereby, the lens 141 is fixed in the accommodating room 111. In operation, the LED lamps 122 are powered for illuminating. Whereby, the projecting unit 13 condenses and projects the light through the lens 141 of the cover unit 14 for lighting a working surface.
However, in the practical application, each conventional projecting unit offers only a single beam angle. Namely, the illuminant scope provided by the LED member is limited. Thus, although the projecting unit could be detachably disposed on the holding plate of the circuit unit, and although the dispositions of the projecting unit as well as the LED lamps are designed individually replaceable, another projecting unit that renders a different beam angle is needed for changing the beam spread while users want to adjust the lighting scope of the lamp or the beam angle of the light. Accordingly, if users want to freely adjust the beam spread of the LED lamp, they have to prepare various projecting units that offer several different beam angles, and moreover, they have to detach the cover unit so as to suitably replace the desirable projecting unit. Obviously, the replacement of the projecting unit is complicated. In addition, after a long time of repeatingly replacement, the gasket placed between the casing unit and the inner cover may be subject to the elastic fatigue. As a result, the lens may not provide a preferable tight joint with the projecting member anymore, and the luminaire efficiency of the LED lamp might be influenced.